Aromatic imide-based dispersant for carbon nanotubes and carbon nanotube composition comprising the same

ABSTRACT

Disclosed herein are an aromatic imide-based dispersant for CNTs and a carbon nanotube composition comprising the same. Having an aromatic ring structure advantageously realizing adsorption on carbon nanotubes, the dispersant, even if used in a small amount, can disperse a large quantity of carbon nanotubes.

This non-provisional application is a divisional of U.S. applicationSer. No. 12/788,793, filed on May 27, 2010, which is a divisional ofU.S. application Ser. No. 11/562,208, filed on Nov. 21, 2006, now U.S.Pat. No. 7,754,881, issued Jul. 13, 2010, which claims priority toKorean Patent Application No. 10-2006-0006852, filed on Jan. 23, 2006,and all the benefits accruing therefrom under 35 U.S.C. §119(a), thedisclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an aromatic imide-based dispersant forcarbon nanotubes and a carbon nanotube composition comprising the same.More particularly, the present invention relates to an aromaticimide-based dispersant having a heterocyclic ring which is readilyadsorbed on the surface of carbon nanotubes to prevent the aggregationof the carbon nanotubes and thus improve the dispersibility of thecarbon nanotubes, and a nanotube composition comprising the same.

2. Description of the Related Art

Since their discovery by Dr. Sumio Iijima in 1991, carbon nanotubes(“CNT”), which are materials having a nanometer-scale size (“nano-size”)have been much studied. A CNT is a honeycomb lattice of carbon atomsrolled into a cylinder, in which one carbon atom is connected withothers in a hexagonal pattern. The hexagonal patterns may beinterspersed with pentagonal shapes which can impart a chiral pattern tothe hexagonal lattice. Having a diameter on the order of a fewnanometers, a CNT exhibits characteristic electrochemical properties.

It is known that the electrical properties of CNT are determined as afunction of structure and diameter (Phys. Rev. B46, 1804 (1992); Phys.Rev. Lett. 68, 1579 (1992)). Depending on the structure of a CNT and itsdiameter, it can behave either as an insulator, a semiconductor or ametal. For example, when the motion of free electrons is changed in CNTby modifying the spin or chirality of the CNT, the free electrons eitherfreely move therein, thereby transforming the CNT into a conductor, orencounter a barrier to flow, thereby transforming the CNT into asemiconductor.

Thanks to superiority in mechanical strength and chemical stability,changeability between semiconductive and conductive properties, andstructural characteristics of narrow, long, and hollow tubes, CNTs arehighly useful when applied to nano-size electronic elements, includingflat display devices, transistors, and the like, as well as to energystorage devices.

When used to form electroconductive films or in the fabrication ofvarious electronic devices, CNTs need to be effectively dispersed inmatrices such as solutions or binders. However, CNTs show great tendencyto aggregate into bundles in a matrix owing to Van der Waals force, andthus the solubility of the nanotubes in water or other solventsdecreases, resulting in processing difficulty.

When aggregated in a matrix rather than dispersed, carbon nanotubescannot exhibit characteristic useful properties and/or cannot be formedinto a film which has uniform properties throughout.

This strong tendency toward aggregation makes it difficult to adequatelydisperse CNTs in a matrix with conventional commercially availabledispersants. Extensive attempts have been made to develop noveldispersants or methods for uniformly dispersing CNTs in solvents orbinders.

For instance, Korean Patent Laid-Open Publication No. 2001-102598discloses a method of introducing an alkyl group into a CNT by achemical linkage. An alkyl group having 8 or more carbon atoms canincrease the solubility of CNTs in organic solvents to hundreds of ppmby weight, but also increases the insulative properties, therebydecreasing electroconductivity. One the other hand, a smaller alkylgroup cannot adequately increase the solubility of the CNT to thedesired extent while maintaining electroconductivity.

Korean Patent Laid-Open Publication No 2003-86442 discloses a method ofwrapping CNTs with a polymer which is physically interactive with thenanotubes, thereby increasing the solubility thereof. However, the CNTswrapped with the polymer are disconnected with each other so that theelectroconductivity decreases. Further, in the absence of a perfectcoating, the polymers as well as the carbon nanotubes can aggregate,leading to a decrease in the efficiency of the dispersant.

In Korean Patent Laid-Open Publication No. 2005-97711, a functionalgroup selected from among cyanate, amine, hydroxy, carboxyl, halide,nitrate, thiocyanate, thiosulfate, vinyl, and combinations thereof isattached to CNTs. This method, however, injures the surface of carbonnanotubes and thereby degrades the electrical properties thereof.

Japanese Patent Laid-Open Publication No. 11-286489 discloses apherylene compound which has improved coloristic and rheologicalproperties, and a pigment preparation. U.S. Pat. No. 5,264,034 alsodiscloses a pigment preparation based on a pherylene compound. However,neither coloristic pherylene pigment, addresses improved dispersibilityof CNTs.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and in an embodimentsdispersant for CNTs is provided, which can prevent the aggregation ofCNTs and thus improve the dispersibility of carbon nanotubes in amatrix.

In another embodiment, a carbon nanotube composition is provided inwhich carbon nanotubes are well dispersed, thereby assuring exhibitionof their properties.

In order to accomplish the above, in an embodiment, an aromaticimide-based dispersant for CNTs is selected from the group consisting ofcompounds represented by the following Chemical Formulae 1 to 4:

wherein,

X is N,

Y is O or S,

is a monocyclic or polycyclic aromatic group selected from

is a polycyclic aromatic group selected from

and

R is selected from the group consisting of polymethylmethacrylate,polybutylacrylate, polyacrylic acid, polymethacrylic acid, a copolymerof polyalkylmethacrylate and polymethacrylic acid, polyoxyethylene,polyoxypropylene, polyvinylalcohol, and polyacrylamide.

In accordance with another embodiment, a carbon nanotube compositioncomprises an aromatic imide-based dispersant, a CNT, and a solvent.

In accordance with another embodiment, a carbon nanotube film comprisesa carbon nanotube, and an aromatic imide-based dispersant.

In accordance with another embodiment, a method of preparing a carbonnanotube film comprises dispersing a carbon nanotube in a solvent withan aromatic imide-based dispersant to form a carbon nanotubecomposition, and coating the carbon nanotube composition on a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill be more clearly understood from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of the operation of an exemplary dispersant;

FIG. 2 is a schematic view showing a CNT having a dispersant adsorbedthereon;

FIGS. 3 a-3 c are ¹H-NMR of exemplary intermediates for the dispersantproduced in the course of the synthesis of the dispersant; and

FIG. 4 is a graph showing the comparison of absorbance at 750 nm betweenthe exemplary dispersant of Example 1 and of Comparative Example 1.

DETAILED DESCRIPTION OF THE INVENTION

Below, a detailed description is given of the present invention withreference to the accompanying drawings.

It will be understood in the following disclosure of the presentinvention, that as used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprise”, “comprises”, and “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, components, and combination of the foregoing, butdo not preclude the presence and/or addition of one or more otherfeatures, integers, steps, operations, elements, components, groups, andcombination of the foregoing.

It will be understood that when an element is referred to as being “on”another element, or when an element is referred to as being “disposedbetween” two or more other elements, it can be directly on (i.e., in atleast partial contact with) the other element(s), or an interveningelement or elements may be present therebetween. In contrast, when anelement is referred to as being “disposed on” another element, theelements are understood to be in at least partial contact with eachother, unless otherwise specified. Spatially relative terms, such as“between”, “in between” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. The device may be otherwiseoriented (rotated 90 degrees, inverted, or at other orientations) andthe spatially relative descriptors used herein interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The aromatic imide-based dispersant has one of the structuresrepresented by the following Chemical Formulae 1 to 4:

wherein,

X is N

Y is O or S,

is a monocyclic or polycyclic aromatic group selected from

is a polycyclic aromatic group selected from

and

R is selected from the group consisting of polymethylmethacrylate,polybutylacrylate, polyacrylic acid, polymethacrylic acid, a copolymerof polyalkylmethacrylate and polymethacrylic acid, polyoxyethylene,polyoxypropylene, polyvinylalcohol, and polyacrylamide.

A CNT has π electrons on the surface thereof. Because the dispersant isa heterocyclic ring structure that is readily coupled with CNTs throughπ −π interaction, it can be adsorbed on CNTs, thereby dispersing them inmatrices. That is, if the π −π interaction between a dispersant and aCNT is stronger than that between CNTs, the dispersant breaks upaggregates of CNTs and thus scatters (i.e., disperses) CNTsindividually.

Generally, however, there is a weak π −π interaction between a CNT and adispersant. When a π −π interaction between a dispersant and CNT doesnot significantly differ from that between CNTs, the dispersant exertsonly limited dispersibility on CNTs.

As for an n-type semiconductor, its structure consists of aromatic ringsthat can form π −ππinteractions. When such an n-type semiconductor isadsorbed on a CNT, charge transfer occurs from the CNT to the n-typesemiconductor, generating a certain quantity of positive charge in theCNT. The orbital hybridization of the CNT delocalizes the positivecharge over the surface of the CNT. Accordingly, the delocalizedpositive charge causes electrostatic repulsion between the CNTs(repulsive force between positively charged CNTs). In addition, havingan amine group capable of bonding with a carboxyl group, which is afunctional group reactive to CNTs, the dispersant has high affinity forCNTs.

Referring to FIG. 1, the dispersant 102 prevents (i.e., restrains) CNTsfrom aggregating in a solvent, and can break up aggregated CNTs 100 intodispersed CNTs 101. In this way, CNTs can be solubilized at a highconcentration in the solvent without degrading electrical, physical, andother properties of the CNTs, such as electroconductivity.

FIG. 2 shows a CNT 200 with the aromatic imide-based dispersant 201 ofthe present invention adsorbed thereon. The adsorption of the aromaticimide-based dispersant 201 onto CNT 200 results from a π −π interactiontherebetween, which leads to the solubilization of the CNT.

Examples of the aromatic imide-based dispersant useful in the presentinvention include compounds represented by the following ChemicalFormulae 5 to 8:

wherein n is an integer from 4 to 15;

wherein n is an integer from 4 to 15;

wherein n is an integer from 4 to 15; and

wherein n is an integer from 4 to 15.

The aromatic imide-based dispersant can be synthesized as follows. In anembodiment, an alkyl chain having a terminal OH group (“ROH”) isconverted to a leaving group by treatment with a sulfonyl chloride anddisplaced with a —CN group (“RCN”) or —N₃ group (“RN₃”) which is thenconverted to —NH₂ to form the amine-terminated chain RNH₂. This chain isreacted with an aromatic carboxyl anhydride to form an imide as shown inReaction Formula 1.

In another embodiment, a carbon nanotube composition includes thearomatic imide-based dispersant. The carbon nanotube composition thuscomprises a carbon nanotube, the aromatic imide-based dispersant, and asolvent. Carbon nanotube films prepared from the carbon nanotubecomposition, in which the carbon nanotubes are uniformly dissolved inthe solvent with the aid of the aromatic imide-based dispersant, canfind a broad variety of applications including transparent conductivefilms, organic solar cells, electrode materials for batteries, and thelike.

The carbon nanotube composition comprises the aromatic imide-baseddispersant in an amount of 0.001 to 10 wt %; a carbon nanotube in anamount from 0.01 to 5 wt %; and a solvent, based on the total weight ofcarbon nanotube, aromatic imide-based dispersant, and solvent. In anembodiment, in the carbon nanotube composition, the carbon nanotube ismixed in a weight ratio of 1:0.001 to 1:10 with the aromatic imide-baseddispersant. The carbon nanotube composition may optionally comprise abinder and/or other organic additives, present in an amount such thatthe desired properties of a carbon nanotube film prepared therefrom arenot substantially adversely affected.

Different types of carbon nanotubes are useful for the carbon nanotubecomposition. In an embodiment, the carbon nanotube contained in thecarbon nanotube composition may be selected from: a single wall carbonnanotube, a double-wall carbon nanotube, a triple-wall carbon nanotube,a quadruple-wall carbon nanotube, a carbon nanohorn, a carbon nanofiber,and combinations thereof. It will be understood that useful carbonnanotubes are exemplified by, but are not limited to, the foregoing listof carbon nanotubes.

Exemplary solvents useful in the carbon nanotube composition includeaqueous based solvents including water; alcohbls, such as methanol,ethanol, isopropyl alcohol, propyl alcohol, butanol, terpineol, and thelike; ketones, such as acetone, methylethyl ketone, ethyl isobutylketone, methyl isobutyl ketone and the like; ethyleneglycols, such asethyleneglycol, ethyleneglycol methylether, ethyleneglycolmono-n-propylether, and the like; propyleneglycols, such aspropyleneglycol, propyleneglycol methylether, propyleneglycolethylether, propyleneglycol butylether, propyleneglycol propylether, andthe like; amides, such as dimethylformamide, dimethylacetamide, and thelike; pyrrolidones, such as N-methyl-2-pyrrolidone (“NMP”),N-ethylpyrrolidone and the like; hydroxyesters, such as lactic acidmethyl ester, lactic acid ethyl ester, β-methoxyisobutyric acid methylester, α-hydroxyisobutyric acid methyl ester and the like; sulfoxidessuch as dimethylsulfoxide; lactones such as γ-butyrolactone; anilines,such as aniline, N-methylaniline and the like; hydrocarbons such ashexane; halogenated solvents such as chloroform; aromatic solvents suchas toluene; and glycol esters such as propylene glycol monomethyl etheracetate (“PGMEA”); and a combination comprising at least one of theforegoing solvents, but are not limited thereto.

Using a mixing or a kneading apparatus, such as an ultrasonicator, ahomogenator, a spiral mixer, a planetary mixer, a disperser, a blendingmixer, or the like, the carbon nanotube and the dispersant may bedispersed by mixing in the solvent to prepare the carbon nanotubecomposition.

The carbon nanotube composition can disperse the carbon nanotubes in amatrix, such as in a solution or a binder, without degrading (i.e.,significantly adversely affecting) the electrical and optical propertiesof the carbon nanotubes themselves. The carbon nanotube composition thusenjoys the advantage of having superior conductivity, film formation,and moldability in addition to showing excellent dispersion stability,such that the carbon nanotubes are neither separated from the solventnor aggregate for a long period of time.

A simple coating technique, such as spin coating, electrophoreticdeposition, inkjet printing, or the like, may be used to apply thecarbon nanotube composition to a substrate.

Thus, a carbon nanotube film comprises a carbon nanotube, and anaromatic imide-based dispersant. In addition, a method of preparing acarbon nanotube film comprises dispersing a carbon nanotube in a solventwith an aromatic imide-based dispersant, to form a carbon nanotubecomposition, and coating the carbon nanotube composition on a substrate.The solvent may then be removed by drying to form the carbon nanotubefilm.

Applications of the carbon nanotube composition may be found inPreparing electronic devices including transparent electrodes fordisplays, such as field effect displays (“FEDs”), light emittingdisplays (“LEDs”), and liquid crystal displays (“LCDs”), organictransistors, wiring materials, smart cards, antennae, electrical cells,fuel cells, capacitors or inductors for printed circuit boards (“PCBs”),electromagnetic shielding films, luminescent materials, bufferingmaterials, electron transporting materials, hole transporting materials,and the like.

A better understanding of the present invention may be realized with thefollowing examples, which are set forth to illustrate, but are not to beconsidered as limited thereto.

EXAMPLES Synthesis Example: Synthesis of Aromatic Imide-Based Dispersant

The aromatic imide-based dispersant of Chemical Formula 1 wassynthesized according to the reaction scheme represented by thefollowing Reaction Formula 2.

Synthesis of Compound 1

To THF (600 ml) was added poly(ethylene glycol) monomethyl ether(“PEGME”, Mw=350, 70 g) and triethylamine (30.7 ml, 220 mmol) and thesolution was cooled to 0° C. Methanesulfonyl chloride (17 ml, 220 mmol)was slowly added over the 1 hour period during which the reactionproceeded. After the reaction was terminated, the solution was filteredthrough a celite pad. The filtrate was extracted with CH₂Cl₂, and driedto afford Compound 1 as a yellow liquid. (85 g, Yield 95%).

Synthesis of Compound 2

To a solution of sodium azide (55.6 g, 855 mmol) in dimethyl acetamide(270 ml), Compound 1 (85 g, 190 mmol) was added dropwise over 30 min.After reacting at 100° C. for 16 hours, the solution was extracted withCH₂Cl₂. Vacuum removal of dimethylacetamide produced Compound 2 as ayellow liquid. (75 g, yield 96%).

¹H NMR (δ, CDCl₃): 3.38 (s, 3 H), 3.49 (m, 2H), 3.6˜3.7 (m, 14H). (SeeFIG. 3 a).

Synthesis of Compound 3

To ethanol (400 ml) were added Compound 2 (75 g, 183 mmol) and Zn dust(36 g, 549 mmol) and the solution was cooled to 0° C. 10N HCl (aq) (54.9ml) was slowly added with the temperature maintained. Reaction wasconducted for 5 hours at the same temperature, followed byneutralization with NaOH (aq) and then extraction with CH₂Cl₂. Removalof the solvent produced Compound 3 as a yellow liquid (50 g, yield 71%).

¹H NMR (δ, CDCl₃): 2.86 (m, 2H), 3.38 (s, 3 H), 3.50 (m, 2H), 3.6 (m,14H). (See FIG. 3 b).

Synthesis of Compound 4

Compound 3 (15.3 g, 40 mmol), 3,4,9,10-pherylene-tetracarboxylicanhydride (4 g, 10 mmol), imidazole (1.9 g, 29 mmol), and Zn(OAc)₂ (0.4g, 2.2 ml) were combined and reacted at 160° C. for 16 hours in an argonatmosphere. The reaction proceeded as the solids were melted by heat.Following reaction termination, the addition of 6N HCl(aq) (60 ml) andethanol (60 ml) and the extraction with CH₂Cl₂ were conductedsequentially. The extract was purified by silica gel columnchromatography (2% methanol in CH₂Cl₂) to afford Compound 4 as a reddishsolid (9.2 g, Yield 82%).

¹H NMR (δ, CDCl₃): 3.36 (m, 3 H), 3.54 (m, 2H), 3.6 (m, 14H), 3.74 (m,2H), 3.87 (t, 2H), 4.46 (t, 2H), 8.38 (d, 2H), 8.52 (d, 2H). (See FIG. 3c).

Example 1

In 20 g of terpineol was dissolved 200 mg of the aromatic imide-baseddispersant of Compound 4, synthesized in Synthesis Example, followed bythe addition of 2 mg of a single-wall CNT to the solution. After beingtreated for 10 hours in a sonic bath to disperse the CNT, the solutionwas centrifuged at 5,000 rpm for 5 min to yield a carbon nanotubesolution as a supernatant. The carbon nanotube solution was measured forabsorbance at 750 nm using UV-Vis-spectroscopy (JASCO(V-560) (Absorbancemode, Scanning speed: 400 nm/min), and the results are shown in FIG. 4.

Comparative Example 1

In 20 g of terpineol was dissolved 200 mg of the dispersant of ChemicalFormula 9 (shown below), and 2 mg of a single-wall carbon nanotube wasadded to the solution, followed by dispersing the nanotube for 13 hoursin a sonic bath (35 kHz, 400 W). The solution was centrifuged at 5,000rpm for 5 min to yield a supernatant. This was measured for absorbanceat 750 nm through UV-Vis-spectroscopy (JASCO V-560) (Absorbance mode,Scanning speed: 400nm/min) and the results are shown in FIG. 4.

As shown in FIG. 4, a higher absorbance was realized by the aromaticimide-based dispersant of Example 1 than by the dispersant ofComparative Example 1, showing that the carbon nanotube was dispersed ata higher concentration. In detail, the aromatic imide-based dispersantdisperses at 4 to 4.5-fold higher efficiency than does the conventionaldispersant of Chemical Formula 9.

The aromatic imide-based dispersant for carbon nanotubes in accordancewith the present invention has an aromatic ring structure which isadvantageous with respect to π −π interaction with carbon nanotubescompared to conventional dispersants. Accordingly, even a small amountof the aromatic imide-based dispersant can disperse a large quantity ofcarbon nanotubes. In addition, the aromatic imide-based dispersant canform a composite with CNTs in a dispersed state.

Having high dispersibility, the carbon nanotube composition ensures theprovision of carbon nanotubes having characteristic electrochemicalproperties and can be formed into a thin film having uniform propertiesthroughout.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible. Accordingly, the modifications, additions and substitutionsshould be understood as falling within the scope and spirit of theinvention.

1. An aromatic imide-based dispersant represented by Chemical Formula 7:

wherein n is an integer from 4 to
 15. 2. A carbon nanotube compositioncomprising an aromatic imide-based dispersant, a carbon nanotube, and asolvent, the aromatic imide-based dispersant being represented byChemical Formula 7:

wherein n is an integer from 4 to
 15. 3. The carbon nanotube compositionas set forth in claim 2, wherein the composition contains the aromaticimide-based dispersant in an amount from 0.001 to 10 wt %, the carbonnanotube in an amount from 0.01 to 5 wt %, and the solvent based on thetotal weight of aromatic imide-based dispersant, carbon nanotube, andsolvent.
 4. The carbon nanotube composition as set forth in claim 2,wherein the carbon nanotube is mixed at a weight ratio of 1:0.001 to1:10 with the aromatic imide-based dispersant.
 5. The carbon nanotubecomposition as set forth in claim 2, wherein the carbon nanotube isselected from a group consisting of a single-wall carbon nanotube, adouble-wall carbon nanotube, a triple-wall carbon nanotube, aquadruple-wall carbon nanotube, a carbon nanohorn, a carbon nanofiber,and combinations thereof.
 6. The carbon nanotube composition as setforth in claim 2, wherein the solvent is selected from the groupconsisting of aqueous based solvents; alcohols; ketones;ethyleneglycols; propyleneglycols; amides; pyrrolidones; hydroxyesters;sulfoxides; lactones; anilines; hydrocarbons; halogenated solvents;aromatic solvents; glycol esters; and a combination comprising at leastone of the foregoing solvents.
 7. The carbon nanotube composition as setforth in claim 6, wherein the solvent is selected from the groupconsisting of water, methanol, ethanol, isopropyl alcohol, propylalcohol, butanol, terpineol, acetone, methylethyl ketone, ethyl isobutylketone, methylisobutyl ketone, ethyleneglycol, ethyleneglycolmethylether, ethyleneglycol mono-n-propylether, propyleneglycol,propyleneglycol methylether, propyleneglycol ethylether, propyleneglycolbutylether, propyleneglycol propylether, dimethylformamide,dimethylacetoamide; N-methyl-2-pyrrolidone(NMP), N-ethylpyrrolidone,dimethylsulfoxide, γ-butyrolactone, lactic acid methyl ester, lacticacid ethyl ester, β-methoxyisobutyric acid methyl ester, andα-hydroxyisobutyric acid methyl ester, aniline, N-methylaniline, hexane;chloroform; toluene; propylene glycol monomethyl ether acetate (PGMEA)and a combination comprising at least one of the foregoing solvents. 8.A carbon nanotube film comprising a carbon nanotube, and an aromaticimide-based dispersant represented by Chemical Formula 7:

wherein n is an integer from 4 to
 15. 9. A method of preparing a carbonnanotube film comprising: dispersing a carbon nanotube in a solvent withan aromatic imide-based dispersant represented by Chemical Formula 7, toform a carbon nanotube composition:

wherein n is an integer from 4 to
 15. 10. The method as set forth inclaim 9, wherein dispersing is accomplished by mixing using an apparatusincluding an ultrasonicator, a homogenator, a spiral mixer, a planetarymixer, a disperser, or a blending mixer.
 11. The method as set forth inclaim 9, wherein casting is accomplished using a coating techniquecomprising spin coating, electrophoretic deposition, or inkjet printing.12. A carbon nanotube film prepared by the method as set forth in claim9.